This invention relates generally to a full opening check valve and in one particular application concerns a downhole blowout preventer which may be inserted into a casing string of an oil and gas well and conventionally cemented into the well and which may be used in conjunction with conventional surface blowout preventers.
Blowout preventers such as the commonly used ram type mounted at the surface of the earth are required both by good drilling practice for enhanced safety, environmental protection and economical operation and by government regulation. However it is desired to augment the protection of a surface mounted blowout preventer with a downhole blowout preventer which will permit the removal and insertion of conventional well tools and the conventional upward annular flow of drilling fluids.
Prior attempts to construct a successful downhole blowout preventer have not solved this problem. For example, Smith U.S. Pat. No. 2,647,728, discloses a depending hollow rubber cone device for insertion into a drill string. The bore through the cone permits the conventional downward flow of drilling fluids through the drill string, but when any reverse flow is encountered, the cone will collapse thereby preventing upward flow. The Smith device does not have the ability to permit upward flow at ordinary velocities while preventing upward flow at increased velocities which is essential to a blowout preventer designed for operation in the annulus surrounding the drill string.
Strickland U.S. Pat. No. 4,308,918, discloses an elongated sliding collar member located around a section of drill pipe. An upper rubber portion of the collar is expandable to casing diameter when the sudden pressure surge of a blowout urges the collar upward over a plurality of tapering wing flanges mounted to the drill pipe above the collar. Strickland U.S. Pat. No. 4,295,529, discloses a downhole blowout preventer having two circumferential drill stem mounted assemblies each of which partially blocks the annular space. Upward motion of the lower assembly responsive to a sudden pressure surge moves it into contact with the upper assembly where the two combine to substantially block the annulus. Both of the Strickland blowout preventers suffer the disadvantage of reducing the annular flow area at the blowout preventer, thus risking the sealing of the annulus by the action of well fluids and the solids suspended therein under normal operating conditions in the absence of a blowout. Additionally, since both are drill string mounted units, neither can act to prevent a blowout when the drill string has been pulled from the well.
Other downhole devices such a packers disclose expandable sleeves for blocking an annular space, such as are disclosed in Lynes U.S. Pat. No. 3,235,017, Brown U.S. Pat. No. 3,068,942, Lynes U.S. Pat. No. 2,997,107, Tamplen U.S. Pat. No. 3,784,214, Layne et al. U.S. Pat. No. 2,082,113, Alley U.S. Pat. No. 2,217,038, and Bettis U.S. Pat. No. 2,125,665. Page U.S. Pat. No. 3,050,132 discloses an inwardly acting pressure operated mechanical shut off for a drill string, while McMurry U.S. Pat. No. 3,601,191 and Pranger U.S. Pat. Nos. 2,303,090 and 2,243,439 disclose bellows-like constructions.
The Layne et al. U.S. Pat. No. 2,082,113 discloses well packer for sealing between a pipe or casing and a well bore. The packer of Layne et al. includes a pipe with a tubular mandrel telescopingly mounted thereto. The pipe and mandrel are held in an axially extended or elongated configuration by a shear pin. The packer also includes a packing element which covers the mandrel and which is attached at one end to the mandrel and at the other end to the pipe. The packer of Layne et al. is set by shearing the shear pin and moving the mandrel telescopingly inward with respect to the pipe, thereby to crumple or fold the packing element about the mandrel. The packing element may include a plurality of axially spaced apart hoops or confining wires for controlling the folding of the packing element. The packer may also include support fingers adjacent either end of the parking element for supporting the parking element during setting.
Therefore, it is an object of the present invention to provide a downhole blowout preventer which will block the annulus of a well bore in response to sustained high velocity upward flow of well fluids through the blowout preventer.
It is a further object of the invention to provide a downhole blowout preventer which may be inserted into a casing string and conventionally cemented into the well bore.
It is a further object of the invention to provide a downhole blowout preventer which will seal the well bore in the absence of a drill string or other well tool within the casing.
It is a further object of the invention to provide a downhole blowout preventer which does not significantly obstruct the annular space or restrict the upward flow of well fluids and suspended solids under ordinary drilling conditions.
It is a further object of the invention to provide a downhole blowout preventer which may be inserted into the well using conventional methods.
It is a further object of the invention to provide a downhole blowout preventer which will permit the insertion and removal of well tools in a conventional manner.
It is a further object of the invention to provide a downhole blowout preventer which will minimize the risk of casing blowout below the surface mounted blowout preventer.
It is a further object of the invention to provide a full opening check valve which will close in response to sustained high-velocity flow through the valve.
It is a further object of the invention to provide a full opening two way check valve which will close in response to sustained high velocity flow through the valve in either direction.